Assessment of microplastic contamination in some commercial fishes of the southern Caspian Sea and its potential risks.

This study examined the occurrence of microplastics (MPs) in the gastrointestinal tract (GIT) of 384 fishes classified into four species from 11 sites in 2022 from the southern part of the Caspian Sea. GITs of fishes were collected and digested in H2O2 and KOH at 45 °C for 72 h. After filtration, extracted MPs were observed under a stereomicroscope, and selected MP particles were identified using FTIR. Presence of MPs was 68.98% in the GIT of the investigated fish. The mean abundance of MPs was 5.9 ± 0.9 MPs/GIT in Rutilus kutum, 9.2 ± 1.2 MPs/GIT in Chelon auratus, 3.6 ± 0.7 MPs/GIT in Alosa braschnikowi, and 2.7 ± 0.5 MPs/GIT in Vimba vimba. The predominant form of MPs was fiber (58.21%), followed by fragment (34.77%). Black (34.4%), white (19.07%), and blue (14.58%) were the most frequently detected colors of MPs. Overall, 6 MP polymers were identified, dominantly polypropylene (42.86%), polystyrene (17.86%), and cellophane (14.28%). The western part of the Caspian Sea (mostly tourist spots and urban areas) showed more MP pollution in fish compared to the eastern part. Polymer hazard index (PHI) revealed alarming microplastic contamination in the southern Caspian Sea. The PHI value of the present study showed that PES (PHI = 8403.78) and PS (PHI = 535.80) were "Extreme danger" and "Danger" risk categories, respectively.

Spatial and temporal distribution of physicochemical parameters of water in Gorgan Bay (the southeast of the Caspian Sea - Iran): Fundamentals for the monitoring of the Caspian Sea coastal areas.

Gorgan Bay as a main part of the Miankaleh (a natural biosphere reserve registered by UNESCO) is one of the richest ecological area in the West Asia and very important internationally recognized refuge for the wildlife. To date, multi physicochemical parameters have not been examined on a large scale. To fill this knowledge gap, the present study aimed to explore the seasonal and spatial variability of water quality parameters of the bay. The results showed that except for depth and transparency, there are significant variations in most parameters across the four seasons. The patterns of these changes in the bay vary, as evidenced by a comparison of the distribution maps of the various factors throughout the year. Notably, alkalinity declined from east to west, reaching its highest levels at important entry points such as the Qarasu River, Bandar-Gaz, and the pier. TDS, on the other hand, increased westward, reaching its highest concentration in the shallow western regions. Maximum depth (310 cm) and transparency (250 cm) were observed in the central bay. While the pH was higher in deeper areas, the distribution of PO4 was more uniform. With lower levels in the east (salinity = 0.40 ‰) and higher levels in the west (salinity = 28.9 ‰), the salinity showed a coherent gradient. Agricultural land use in the basin of the bay and fluxes of nutrients and sediments of the rivers entering the bay has significant contribution to the bay pollution situation. These results will serve as a guide for improving our understanding of the Gorgan Bay ecosystem. They also have implications for informed conservation and management plans adapted to the specifics of this special region within the Caspian Sea.

Biochemical biomarkers of skin mucus in Neogobius melanostomus for assessing lead pollution in the Gulf of Gorgan (Iran).

The present study was conducted to provide basic information on the physiological damages (mucosal indicators) of Round Goby under laboratory and environmental conditions of lead contamination. The other goal was to find mucosal biomarkers of lead contamination in the Gulf of Gorgan. In the laboratory study, 400 pieces of fish with an average the weight of 35 ± 7.16 g were caught alive and were exposed to lead concentrations of 0, 3.75, 7.5 and 15 mg / l for 14 days. Once the experiment was completed, the samples of mucus and liver were collected from the fish samples with the samples being surveyed by analyses of SDS-PAGE, mucus safety and toxicology. In the field test, the samples of fish, water, and sediment were prepared from four stations. In addition to measuring the lead in water, sediment and liver tissue, the samples of mucus from the caught fish were similarly analyzed under the laboratory conditions mentioned. According to the results under laboratory conditions, obvious differences were observed between the protein pattern of samples of treatment with the control group. Further, among innate immune parameters of the mucus, only lysozyme showed a significant correlation with the concentrations of lead accumulated in the liver of Round Goby (P < 0.05). Under environmental conditions, obvious differences were also observed between the protein pattern of samples of contaminated stations with the control station. Further, among innate immune parameters of the mucus, lysozyme indicated a positive correlation while alkaline phosphatase showed a negative correlation with lead contamination in the liver of Round Goby (P < 0.05). In total, in the pattern of mucus protein, the intensity of the band within the range of 25 kDa was enhanced in both conditions, suggesting the presence of proteases in this region. Also, among the immune parameters, lysozyme enzyme showed a significant and positive correlation with liver lead contamination in both conditions (P < 0.05). These can be considered as the biomarkers of protein pattern and safety in Round Goby mucus for assessing lead pollution in Gulf of Gorgan.

Biofloc technology improves growth, innate immune responses, oxidative status, and resistance to acute stress in common carp (Cyprinus carpio) under high stocking density.

This study aimed to evaluate the effects of biofloc technology (BFT) on the performance of common carp under high stocking density. Fish (8.41 ±â€¯0.44 g) were stocked into 12 tanks (70 L) in a 2 × 2 factorial design consisting of clear water (CW) and BFT systems at two stocking densities. Fish were divided into four groups according to culture system and stocking density: CW6 (clear water, 6 kg m-3), CW12 (clear water, 12 kg m-3), BFT6 (biofloc, 6 kg m-3), and BFT12 (biofloc, 12 kg m-3). After 49 days, the fish were exposed to acute crowding stress (40 kg m-3) for 7 days to evaluate the fish performance to additional stressors. Total ammonia nitrogen (TAN) concentration was significantly lower in BFT groups at the end of the trial. The growth of fish was significantly higher and the feed conversion ratio was lower in BFT groups. The final density of fish was highest in BFT12 group (25.41 ±â€¯0.48 kg m-3). The amylase and protease activities in BFT groups were significantly higher than the CW12 group. The highest serum catalase, superoxide dismutase, and glutathione peroxidase activities, and malondialdehyde content (3.07 ±â€¯0.16 nmol mg-1 protein) were observed in CW12 group. Serum LDL, cholesterol, triglyceride, total protein, and albumin levels were significantly higher in CW6 and BFT6 groups, followed by BFT12 group, and lowest in CW12 group. Serum globulin level was lowest in CW12 group (0.68 ±â€¯0.06 g dL-1). After 49 days, serum lysozyme, alternative complement (ACH50) and ALP activities were significantly higher and serum cortisol and glucose levels and ALT and AST activities were lower in BFT groups than the CW12 group. After 7 days of acute stress, serum lysozyme activities were significantly lower and ACH50 and ALP activities were higher in BFT groups than the CW12 group. Also, fish in CW12 group were more sensitive to the acute stressor, showing higher cortisol and lower glucose levels. Overall, biofloc had the anti-stress effect, and the culture of common carp in the biofloc system at a stocking density of 12 kg m-3 could be recommended. BFT can also exert beneficial effects on the welfare of fish subjected to acute stress.

Determination of toxic (Pb, Cd) and essential (Zn, Mn) metals in canned tuna fish produced in Iran.

BACKGROUND: Metal pollution of waterways directly affects human health and can impact the food chain. Seafood living in polluted water can accumulate trace metals. The purpose of this study was to analyze the toxic metals Pb and Cd and the dietary essential metals Zn and Mn in 120 cans of tuna species from four different brands processed in Iran and purchased in 2012. RESULTS: The mean level of metals for each brands of canned fish obtained in mg/kg were as follows: yellowfin tuna (Pb: 0.19 ± 0.015, Zn: 5.77 ± 4.17, Mn: 0.08 ± 0.07, Cd: 0.15 ± 0.12), Kilka (Pb: 0.95 ± 0.88, Zn: 30.47 ± 29.82, Mn: 1.01 ± 0.73, Cd: 0.07 ± 0.05), Kawakawa (Pb: 0.28 ± 0.23, Zn: 6.77 ± 5.21, Mn: 0.17 ± 0.12, Cd: 0.12 ± 0.09), longtail tuna (Pb: 1.59 ± 1.56, Zn: 7.44 ± 6.11, Mn: 0.04 ± 0.03, Cd: 0.06 ± 0.04). Pb, Zn and Cd levels were generally higher than the FAO/WHO permissible limits (Pb: 0.50 mg/kg, Zn: 50.0 mg/kg and Cd: 0.50 mg/kg) and the European Union acceptable dietary limits. CONCLUSIONS: Based on the United States Environmental Protection Agency health criteria, there is no health risk associated with Mn concentration in the samples analyzed. The limits of detection of the method for Pb, Zn, Mn and Cd in mg/kg were 0.01, 0.5, 0.01 and 0.01, respectively. The result of the one-way analysis of variance suggested significant variations (p < 0.05) in the concentration of the metals in the different types of canned fish with the following being outside of compliance levels.